Slit plants with two or more wires are used to increase the production of wires and/or bars. They provide that, after the passage of the starting billet in one or more rolling cages or units to reach a substantially rectangular section, the rolled section is slit longitudinally into two or more equal parts through the passage within channels made into specially shaped rolling rollers, making two or more rolled sections which move in parallel and consequently creating two or more parallel side by side rolling lines.
In the prior art, the two wires that are created through the process of longitudinal slitting of the rolled section are then processed separately by means of different machinery. This is mainly due to the physical and metallurgical differences that each wire or bar has, with the consequent need to separate the rolled wires or bars to be able to ensure a homogeneous and uniform processing thereof. The two wire slit thus allows increasing the production but also entails a considerably higher cost as regards the machinery, the related spares and the maintenance of what is located downstream of the slitting.
An essential aspect for the cutting and management of the rolling wires or bars consists of the speed and effectiveness of the shear, which must slit with precision and subsequently convey the sections thus obtained without undergoing hitches of a mechanical nature. In the plants currently in operation this aspect, linked to the increasingly growing production, has now taken primary importance and the necessity of having to use a shear for each wire or bar therefore is a considerable limitation and an increase of complexity for both the plant and for the effectiveness of the process itself.
An example of a single machinery to process the two lines is known from document EP0773082, which describes a single shear which cuts two parallel wires. However, the two wires are kept spaced apart and the two lines are separate, thus requiring separate equipment upstream and downstream for the two wires.
Also U.S. Pat. No. 4,966,060 refers to a high-speed shear system for cutting rolling wires or bars wherein a pair of cutting knives acts on each wire or bar while a specially shaped partitioning template allows the cut section of wire to enter output channels. However, the choice of the output channel is governed by the lateral mechanical displacement of the guide, thus slowing down the separation process and with the high risk that the cut wire enters the wrong output channel, or even worse, gets stuck between the partitioning template and the guide itself, thus locking the plant.
Another system for cutting rolling wires is disclosed in document U.S. Pat. No. 5,644,941, which describes a system for cooling and cutting single wires or rods by means of facing pairs of knives. Also in this case, the system is rather complex basically due to the fact that every single wire must be slit and conveyed separately to the output guides, with issues related to the management and the spacing between one wire and the other.
Finally, also U.S. Pat. No. 6,684,745 describes a shear for cutting rolling wires or bars which has, for each of them, different series of coupled knives and a complex system of guides for the management of the cutting and the positioning of the wires themselves. Also for this solution, the major problems are found in the multiplicity of devices in case of different wires and in the difficult management of the cutting tails in output from the shear, which must be conveyed individually in the respective separation channels.